Thursday, April 22, 2010

Fire and ice

This photograph (click to enlarge) of the mischievous Eyjafjallajokull volcano in Iceland, by Marco Fulle of the Osservatorio Astronomico di Trieste, cries out for commentary, but words can add nothing to its beauty. Let it stand, then, as an icon for for the powers of nature -- fire, ice, matter and energy -- over which we have so little control.

Iceland is part of the Mid-Atlantic Ridge, a vast mountain range (mostly submarine) that stretches for thousands of miles down the center of the ocean. Here the crust of the Earth is being lifted and stretched asunder by forces from below. Like other parts of the ridge, Iceland is being torn apart, the cracks filled with lava. The rift valley near the ancient Icelandic capital of Thingveliir has widened by about forty feet in the thousand years since the Norse settled there.

Why so much more volcanic activity in Iceland than at other places along the ridge? Years ago it was proposed that a large meteorite punctured the Earth's crust here, releasing a flood of molten rock from the hot interior. But the chances of a meteorite hitting exactly on an already existing "crack" seems slim indeed. No, Iceland simply sits above an unusually hot "hot spot" in the Earth's mantle, like the big island of Hawaii.

Iceland, of course, is where Professor Lidenbrock chose to begin his Journey to the Center of the Earth, down the throat of another volcano, Snaefellsjokull, eighty miles or so northwest of Reykjavik, after decoding the fateful message in an ancient text:
Descend into the crater of Sneffells Yokul,
over which the shadow of Scartaris falls
before the kalends of July, bold traveler,
and you will reach the center of the earth.
I have done this. Arne Saknussemm.
Lindenbrock's nephew raises all the usual scientific objections -- the interior of the Earth is too hot, and so on -- which the Professor summarily dismisses. And so, down they go with their intrepid Icelandic guide Hans.

Of course, as we now know, the nephew was correct in his objections; descend the apparently extinct Snaefellsjokull and pretty soon you'd meet the fires that stoke Eyjafjallajokull.

Still, science fiction is fun. So how about this. Imagine a hole straight down from Snaefellsjokull to the other side of the Earth, insulated from heat and evacuated of air. No need to tediously descend with Lindenbrock and company. Just jump in (with your air pack). You'd accelerate as you fell, zipping past the center of the Earth at about 18,000 miles per hour, then decelerate until you approached the surface on the other side. Where you'd better grab hold of something before you start the return journey (ignoring the fact that the antipode of Iceland is in the ocean south of Australia). Forty-two minutes. That's how long the journey would take. Twenty-one minutes to the center. Rather faster than Professor Lindenbrock imagined.